The invention herein relates generally to piezoelectrically operated fluid control devices of the type wherein plural cantilever mounted piezoelectric benders cooperate with associated impacting members, respectively to deform a membrane to cover and/or uncover a valve seat upon energization or deenergization, both benders and impacting members being isolated from the fluid by the membrane. In particular, the invention is directed to provision of a mounting for seating the benders on the body of the fluid control device to provide secure, accurate placement of the benders, to permit positional adjustment and, further, to provide means for establishing electrical connection to the benders while maintaining electrical isolation thereof from each other.
It is known also to use a stack of piezoelectric discs or wafers as a driver for an undamped spring-mass system. U.S. Pat. No. 3,614,486 discloses the use of a stack of thin piezoelectric discs as a driver for applications which require high speed, accuracy and no vibration.
The known devices position the piezoelectric member in contact with the fluid and require protective coatings on the piezoelectric beam and electrical connections to protect the same from chemical attack by the fluid. Additionally, mechanical problems result from the fluid contact with the piezoelectric member.
The piezoelectric fluid control device disclosed in my earlier U.S. Pat. No. 4,450,375 included multiple ports each with its own valve seat and an actuator, the valve seats being covered by a common deformable membrane. The benders were provided in the same number as the number of ports to impact on the actuator and deform the membrane changing the condition of the valve. Multiple benders were formed individually or in comb configuration as a laminate comprising at least a pair of flat bonded portions including a layer of ceramic piezoelectric material on a supporting electrically conductive stainless steel or the like member of conforming configuration. The fluid control device was characterized by the isolation of the valve actuator (a spherical object) and piezoelectric bender from the fluid whose flow was being controlled by a common diaphram between the actuator and valve seats.
Only one deformable diaphram was employed. However, the piezoelectric bender of the plural port valve was formed of a comb-like configuration with the arms or bender portions joined along one end by a bridge while the tines extend in a generally common plane when installed, to cooperate with the spherical impacting member to deform only that portion of the common diaphram sealingly engaged over each valve seat. More precision in operation could be obtained if the piezoelectric benders could be individually adjusted. This is enabled by the invention. With such adjustment one can adjust tension, position, etc. for the control of fluid at each valve. Compensation should be provided for fatigue of certain members as well as the differences in force required to be exerted to seat and unseat the various ball valves constituted by the individual impacting members depending upon their position and relative location in the overall valve body.
Proper mounting and relative positioning of individual piezo benders is required if same are to be employed. Secure mounting of each bender and proper angular orientation of each bender at its correct distance from its associated ball or impacting member is essential.
Improved versatility can be obtained if the multiple valve could be operated as a normally open and/or normally closed valve simply by an adjustment of or change in the mounting of the benders. The use of benders in the same print head that operate either as normally closed or normally open valve actuators can be accomplished using individually formed benders disposed to operate one way or the other. Achievement of such versatility is a highly desirable goal provided none of the advantages of the disclosed piezoelectric fluid control device are sacrificed in such achievement.
The fluid control device contemplated is capable of being coupled electrically to an electrical power source. Using multiple tine-like comb units preferably required the electrical connections be made using solder connecting individual electrical leads to the individual benders. High cost is a deterrent to such constructions as is the multiplicity of solder connections required. Of further disadvantage are the failure of the connections equally to withstand fracture attributable to vibration, possibly due to poor soldering, nonuniformity and/or inconsistency in quality of the individual solder connections either in factory or in field handling and operational stress placed thereon, particularly in view of the advantageous high speed use capability. Accordingly, provision of means for effecting an electrical connection in one act by enabling use of a multiple array of printed circuit edge connectors will provide high reliability, economical, positive electrical connection. Additional advantage would be the provision of means rendering one of the benders adjustable independent of others, so that the adjustment of one or more of the benders will not disturb the adjustment of others.
The benders of the piezoelectric fluid control device each operate between two states or conditions, a rest or static condition and a "dynamic" condition, that is, a condition under which the free ends of the benders are moved when electrically energized. It is desirable to mount the fixed ends of the piezoelectric benders in a manner which enables adjustment of the rest or static condition of the bender and adjusting the force exercised by the free end thereof to control the force exercised on the impacting member when the valve is in normally closed condition or to control the force exercised when energized for valves used in a normally open mode.
The characteristics of the valve determine the sealing force required to maintain the valve closed at a given pressure.
It is the intention to provide a singular bender mounting or a multiple bender mounting capable of securing the fixed end of the cantilevered spring-like piezoelectric benders and providing a capability to adjust the force exercizable against the membrane sufficient in respect of a normally open valve operation to overcome the pressure exercised on the membrane by the fluid, when the bender is energized.
It is further intended to provide a mounting which as installed provides a stationary or an adjustable fulcrum point for adjustment and a clamping member cooperating with the fulcrum. The mounting also provides for initial deflection adjustment, the bender being also electrically insulated, i.e. isolated, from adjacent benders. Electrical connection can be effected with cooperating standard printed circuit board edge connectors, a spacer being introduced to compensate for differences in thickness at the connection when the thickness of the normally employed printed circuit board is greater than the thickness of the bender at its fixed end. The mounting and electrical connection are capable of accommodating a single bender, multiple individual benders or a comb-like multiple bender. Where individual mountings are employed, the mounting can include cooperable tongue and grooves to assure alignment and spacing of benders on the valve body relative to the impact members at the valve seats.